1. Field of the Invention
This invention relates to a light emitting apparatus using a light emitting diode element. For example, a light emitting apparatus of the invention is used as illumination light source in vehicle.
2. Description of the Related Art
Surface mount device (SMD) type light emitting diode elements are widely used as a light source such as illumination unit with limited installation space. For example, Japanese patent application laid-open No.6-103802 discloses a vehicle high mount stop lamp that a plurality of SMD type light emitting diode elements are arranged linearly. In this example, lens is disposed to cover each light emitting diode element, and light emitted from the light emitting diode element is converged by the lens function to enhance the directivity of light. On the other hand, Japanese patent application laid-open No.9-102631 discloses a SMD type light emitting diode element used as optical communication module. Also in this case, lens is used to enhance the directivity of light.
The conventional light emitting apparatuses are designed such that the apex (center) of lens is located just over each light emitting diode element and the optical axis of lens coincides with the optical axis of corresponding light emitting diode element. Thus, light emitted from each light emitting diode element passes through the lens, offering circular light. When a plurality of light emitting diode elements are disposed close to each other in order to enlarge the illumination area or to enhance the illumination intensity, lights from the light emitting diode elements are overlapped partially and, therefore, unevenness in illumination intensity occurs. The unevenness in illumination intensity may be solved by using a reflector to promote the diffusion of light. However, since each light emitting diode element is needed to have individual reflector to equalize the illumination intensity of the entire illumination area, the apparatus composition will be complicated and cannot meet a requirement to reduce its size. Even when using the reflector, it is difficult to obtain equalized illumination intensity in the entire illumination area.
Further, in the conventional light emitting apparatuses, one lens (or lens section) is disposed corresponding to one light emitting diode element. Namely, light emitted from one light emitting diode element is radiated outside through corresponding lens. Therefore, the light emitting diode elements have to be at a sufficient distance from each other in order not to generate interference between neighboring lenses. This becomes a restriction in reducing the size.